Aminomethyl-substituted thiazolobenzimidazole compounds

ABSTRACT

This invention relates to the provision of novel aminomethyl-substituted thiazolobenzimidazole derivatives represented by the following general formula (I) or a salt thereof. 
     The aforementioned derivative or a salt thereof has a metabotropic glutamate receptor action and excellent oral activity and is therefore useful as a medicament. 
                         
(In the formula, R 1 : an oxygen-containing saturated hetero ring or the like, Alk 1 : a lower alkylene, m: 0 or 1, Alk 2 : a lower alkylene which may be substituted with oxo group, n: 0 or 1, X: a bond, O, S or NR 5 , R 3 : H or the like, and R 2 , R 4 , R 5 , R 6  and R 7 : the same or different from one another and each represents H or the like.
 
     Provided that R 3  does not represent a lower alkyl or a halogeno-lower alkyl when X is a bond and n is 1. Also, R 4  represents a group other than Me when m is 1, R 1  is OH or OMe and Alk 1  is a C 1-3  alkylene, and further 1) when X is a bond, n is 1 and R 3  is H, or 2) when X is a bond, n is 0 and R 3  is cyclohexane.)

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of PCT Application No. PCT/JP03/03348, filed Mar. 19, 2003, whichclaims priority under 35 U.S.C. 119 to Japanese Application No.2002-77431 filed on Mar. 20, 2002.

TECHNICAL FIELD

This invention relates to novel aminomethyl-substitutedthiazolobenzimidazole derivatives or a salt thereof, which has highsafety and is useful as a medicament.

BACKGROUND OF THE INVENTION

Glutamic acid acts as a neurotransmitter in the mammalian centralnervous system (Mayer M. L. and Westbrook G. L., Prog. Neurobiol., 28(1987) 197-276). By the recent studies, importance of glutamic acid inthe higher order cranial nerve function has been revealed. Glutamic acidis released from the nerve ending and regulates activity of nerve cellsor release of a neurotransmitter, via glutamate receptors which arepresent in the postsynaptic membrane or nerve ending. Based on variouspharmacological and physiological studies, glutamate receptors arecurrently classified roughly into two categories. One of them isionotropic receptor and the other is metabotropic receptor (Hollmann Mand Heinemann S., Annu. Rev. Neurosci., 17 (1994) 31-108).

Based on the molecular biological studies, it has been reported that themetabotropic glutamate receptor (to be referred sometimes to as mGluRhereinafter) exists so far in at least eight different subtypes of frommGluR 1 to mGluR 8. The mGluR is classified into a group of receptors(group I: mGluR 1 and mGluR 5) which accelerate production of inositoltriphosphate (IP3) and incorporation of calcium ions into cells, bycoupling with phospholipase C via G protein, and other groups ofreceptors (group II: mGluR 2 and mGluR 3, group III: mGluR 4, mGluR 6,mGluR 7 and mGluR 8) which inhibit production of cAMP by coupling withGi protein. These receptors show different intracerebral distributionsfrom one another, for example, mGluR 6 does not exist in the brain butexists only on the retina, so that it is considered that each receptoris taking each own different physiological role (Nakanishi S., Neuron,13 (1995) 1031-1037).

Compounds which are selective for the mGluR in comparison with theionotropic receptor have so far been reported (Hayashi Y. et al., Br. J.Pharmacol., 107 (1992) 539-543; Hayashi Y. et al., J. Neurosci., 14(1995) 3370-3377), and relationships between the mGluR and variousmorbid states of diseases have been reported as the following cases (1)to (6), based on the studies carried out using these compounds.

(1) Epilepsy is induced by the administration of an mGluR agonist(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (to be referred to as(1S,3R)-ACPD hereinafter) (Tizzano J. P. et al., Neurosci. Lett., 162(1993) 12-16; McDonald J. W. et al., J. Neurosci., 13 (1993) 4445-4455).In addition, the efficacy of (S)-4-carboxy-3-hydroxyphenylglycine (to bereferred to as (S)-CHPG hereinafter), which is an antagonist of mGluR 1and also an agonist of mGluR 2, in various epilepsy models has beenreported (Dalby, N. O. & Thomsen, C. J., J. Pharmacol. Exp. Ther., 276(1996) 516-522).

(2) Participation of mGluR in the transmission of pain sensation intospinal posterior horn nerve cells has been confirmed byelectro-physiological tests (Young, M. R. et al., Neuropharmacology, 33(1994) 141-144; ibid., 34 (1995) 1033-1041). In addition, it has beenreported that the (S)-CHPG has an action to delay avoiding reaction ofthermal and mechanical pain sensation stimulation (Young, M. R. et al.,Br. J. Pharmacol., 114 (1995) 316P).

(3) It has been reported that when the (1S,3R)-ACPD or an mGluR agonist(RS)-3,5-dihydroxyphenylglycine (to be referred to as 3,5-DHPGhereinafter) is administered in a trace amount or systemically to thecerebral parenchyma of mouse or rat, it causes nerve cell deathaccompanied by spasm (Lipartit, M. et al., Life Sci., 52 (1993) PL85-90; McDonald, J. W. et al., J. Neurosci., 13 (1993) 4445-4455;Tizzano, J. P. et al., Neuropharmacology, 34 (1995) 1063-3067). It isconsidered that this is a result of the activation of mGluR 1 and mGluR5.

(4) It is well known that chronic administration of benzodiazepine formsits dependency. It has been reported that metabolic turnover ofinositol-phospholipid increases by (1S,3R)-ACPD via mGluR, on the secondday and third day after 7 days of continuous administration ofbenzodiazepine, and it has been suggested that mGluR is taking a role inthe expression of benzodiazepine withdrawal syndrome (Mortensen, M. etal., J. Pharmacol. Exp. Ther., 274 (1995) 155-163).

(5) It has been reported thatN-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced substantia nigradopamine nerve cell death is inhibited by the ventricular administrationof a mGluR group I antagonist 1-aminoindane-1,5-dicarboxylic acid(Aguirre, J. A. et al., Neuroreport. 12 (2001) 2615-2617).

(6) It has been reported that an antagonist of mGluR 1 inhibits proteinextravasation outside of dural blood vessels caused by an electricstimulus of trigeminal ganglion (WO 01/32632).

That is, the above reports show that compounds which act upon mGluR 1are useful in epilepsy, pain, nerve cell death inhibition,benzodiazepine withdrawal syndrome and migraine.

Also, since the efficacy of a mGluR 1 antagonist has been confirmed in arat cerebral infarction model, it is considered that the mGluR 1antagonist is useful as a preventive or therapeutic agent for cerebralinfarction (Patent Reference 1).

In addition, since it has been confirmed that a mGluR 1 antagonistimproves reduction of pain threshold in neuropathic pain model, it isalso useful as an agent for treating neuropathic pains such as a painafter shingles, a pain accompanied by diabetic neuropathy, acarcinomatous pain, a postoperative chronic pain and the like (PatentReference 2).

As compounds having mGluR 1 antagonism, thiazolobenzimidazolederivatives are disclosed in the aforementioned Patent References 1,2and 3 and Patent Reference 4.

However, the thiazolobenzimidazole derivatives disclosed in theaforementioned Patent References 1, 3 and 4 are compounds which werefound aimed at cerebral infarction as the principal indication whosemain administration route is parenteral administration.

In addition, it is reported in the Patent Reference 2 thatthiazolobenzimidazole derivatives in which the benzene ring moiety ofthiazolobenzimidazole ring is substituted with substituted orunsubstituted amino group show a neuropathic pain therapeutic effect byoral administration.

[Patent Reference 1]

PCT International Publication Pamphlet WO 99/44639

[Patent Reference 2]

PCT International Publication Pamphlet WO 01/08705

[Patent Reference 3]

PCT International Publication Pamphlet WO 00/59913

[Patent Reference 4]

JP-A-2000-351782

Problems that the Invention is to Solve

The object of the invention is to provide clinically useful novelthiazolobenzimidazole derivatives and a salt thereof, as metabotropicglutamate receptor antagonists having excellent oral activity.

Also, though the compounds of the aforementioned Patent Reference 2 havean oral activity, they also have a carcinogenic action, because it hasbeen confirmed by this firm's studies that they have gene mutagenicity.It is considered that this gene mutagenicity is expressed by astructural characteristic in that they have an aniline amino group, sothat compounds having an aniline amino group have a disadvantage in thatthey cannot be used in clinical tests as a medicament even in case thatthey have an oral activity.

The present inventors have conducted intensive studies with the aim ofsolving the aforementioned problems, and accomplished the invention byfinding that the aminomethyl-substituted thiazolobenzimidazolederivatives of the invention are compounds which have a strong oralactivity as a metabotropic glutamate receptor antagonist and areclinically useful because of no mutagenicity.

In this connection, the compounds of the invention are compounds whichare not illustratively disclosed in the aforementioned Patent References1 and 3, in terms that they have an oxygen-containing saturated heteroring, a sulfur-containing saturated hetero ring or the like, or anaminomethyl group substituted with an alkyl substituted with such asaturated hetero ring, as a substituent group on the benzene ring moietyof thiazolobenzimidazole ring.

Accordingly, the invention relates to aminomethyl-substitutedthiazolobenzimidazole derivatives represented by the following generalformula (I) or a salt thereof and a medicament which uses the same asthe active ingredient.

Illustratively, it relates to an aminomethyl-substitutedthiazolobenzimidazole derivative represented by the following generalformula (I) or a salt thereof

(wherein signs in the formula mean as follows;

-   R¹: an oxygen-containing saturated hetero ring- which may be    substituted, a sulfur-containing saturated hetero ring- which may be    substituted, a cycloalkyl which may be substituted, —O—R⁶ or —S—R⁷,-   Alk1: a lower alkylene,-   m: 0 or 1,-   Alk2: a lower alkylene which may be substituted with oxo group,-   n: 0 or 1,-   X: a bond, O, S or NR⁵,-   R³: H, a lower alkyl, a halogeno-lower alkyl, a lower alkenyl, a    lower alkynyl, a cycloalkyl which may be substituted, cyano or a    saturated hetero ring-, and R², R⁴, R⁵, R⁶ and R⁷: the same or    different from each other and each represents H or lower alkyl, with    the proviso that R³ does not represent a lower alkyl or a    halogeno-lower alkyl when X is a bond and n is 1, and that R⁴    represents a group other than methyl when m is 1, R¹ is OH or a    methoxy and Alk1 is a C₁₋₃ alkylene, and further 1) when X is a    bond, n is 1 and R³ is H, or 2) when X is a bond, n is 0 and R³ is a    cycloalkyl).

Preferred is aminomethyl-substituted thiazolobenzimidazole derivativesor a salt thereof, in which R¹ in the general formula (I) is anoxygen-containing saturated hetero ring- which may be substituted, andR³ is a lower alkyl or a saturated hetero ring-;

more preferred isN-methyl-N-neopentyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide;6-{[(1,3-dioxolan-2-ylmethyl)amino]methyl}-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide;orN-neopentyl-6-({[tetrahydro-2H-pyran-4-yl)methyl]amino)methyl)thiazolo[3,2-a]benzimidazole-2-carboxamideor a salt thereof.

The present invention further relates to a medicament which comprisesthe aforementioned aminomethyl-substituted thiazolobenzimidazolederivative represented by general formula (I) or a salt thereof as theactive ingredient, preferably a mGluR 1 receptor antagonist.

More preferably, it is a pharmaceutical composition having a mGluR 1receptor antagonism, which comprises a mGluR 1 receptorbinding-inhibitory amount of the aforementioned aminomethyl-substitutedthiazolobenzimidazole derivative or a salt thereof.

Further preferably, it relates to a therapeutic agent for a disease inwhich activation of mGluR 1 receptor is concerned, which comprises theaforementioned aminomethyl-substituted thiazolobenzimidazole derivativeor a salt thereof as the active ingredient, illustratively a therapeuticagent for a neuropathic pain.

Best Mode for Carrying Out the Invention

The following further describes the compound of the invention.

In the definition of general formulae as used herein, unless otherwisenoted, the term “lower” means a straight or branched carbon chain havingfrom 1 to 6 carbon atoms.

The “lower alkyl” is a C₁₋₆ alkyl, preferably a straight or branchedC₁₋₄ alkyl such as methyl, ethyl, propyl, isopropyl, t-butyl or thelike, more preferably a C₁₋₃ alkyl.

The “lower alkylene” is a C₁₋₆ alkylene, preferably straight or branchedC₁₋₄ alkylene (e.g, methylene, ethylene, methylmethylene, trimethylene,propylene, ethylethylene, tetrabutylene or the like), further preferablya C₁₋₃ alkylene.

The “lower alkylene substituted with oxo group” means a group in whichan optional carbon atom of a straight or branched C₂₋₆ alkylene amongthe aforementioned lower alkylene groups is substituted with oxo group,and preferred is —CH₂—C(O)—, —C(O)—CH₂—, —CH₂—C(O)—CH₂—, —(CH₂)₂—C(O)—or —C(O)—(CH₂)₂—.

The “lower alkenyl” is a C₂₋₆ alkenyl, preferably straight or branchedC₂₋₄ alkenyl (e.g., vinyl, propenyl, butenyl or the like), morepreferably a C₂₋₃ alkenyl.

The “lower alkynyl” is a C₂₋₆ alkynyl, preferably straight or branchedC₂₋₄ alkynyl (e.g., acetynyl, propynyl, butynyl or the like), morepreferably a C₂₋₃ alkynyl.

The “halogen” means a halogen atom, for example, it means fluorine,chlorine, bromine or iodine atom.

The “halogeno-lower alkyl” means a group in which optional one or morehydrogen atoms of the aforementioned lower alkyl are substituted withthe aforementioned halogen atoms, and trifluoromethyl is desirable.

The “cycloalkyl” means a 3- to 8-membered cycloalkyl, and preferred iscyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl or the like.

The “saturated hetero ring” means a 3- to 8-membered saturated heteroring containing from 1 to 4 hetero atoms selected from nitrogen atom,oxygen atom and sulfur atom, and its examples include pyrrolidine,piperidine, piperazine, homopiperazine, imidazolidine, morpholine,thiomorpholino, oxirane, oxetane, thietane, tetrahydrofuran,tetrahydropyran, [1,3]dioxolan, [1,4]dioxane, tetrahydrothiophene,[1,4]dithian, hexahydroazepin, hexahydro-pyrrolo[2,1-c][1,4]oxazine andthe like.

Preferred is a 5-membered oxygen-containing saturated hetero ring orsulfur-containing saturated hetero ring.

The “oxygen-containing saturated hetero ring” means a saturated heteroring necessarily containing oxygen atom as a hetero atom in the ringamong the aforementioned hetero rings. That is, it means a 3- to8-membered saturated hetero ring which may contain 1 or 2 nitrogen atomor sulfur atom, in addition to 1 to 3 oxygen atoms. Preferred is a 4- to6-membered oxygen-containing saturated hetero ring, and more preferredis oxetane, tetrahydrofuran, 1,3-dioxolan tetrahydropyran, ormorpholine.

The “sulfur-containing saturated hetero ring” means a saturated heteroring necessarily containing sulfur atom as a hetero atom in the ringamong the aforementioned hetero rings. That is, it means a 3- to8-membered saturated hetero ring which may contain 1 or 2 nitrogen atomor oxygen atom, in addition to 1 to 3 sulfur atoms. Preferred is a 4- to6-membered saturated hetero ring, and more preferred is thietane,1,3-dithiolan, tetrahydrothiophene, thiazolidine or thiomorpholine.

The oxygen-containing saturated hetero ring which may be substituted,the sulfur-containing saturated hetero ring which may be substituted andthe cycloalkyl which may be substituted may have 1 to 3 substituentgroups on optional carbon atoms or hetero atoms on the ring.

The substituent group means a usual substituent group of a group to besubstituted commonly used in said field, and its most desirable examplesinclude a halogen, cyano, a halogeno-lower alkyl, a lower alkyl, OH, alower alkyl-O—, oxo, a lower alkyl-C(O)—, carboxyl, a loweralkyl-O—C(O)—, a lower alkyl-O-lower alkyl-, nitro, amino which may besubstituted with 1 or 2 lower alkyl groups, and the like.

Preferred are a lower alkyl and a lower alkyl-O—.

Depending on the kind of groups, the compound of the invention exists inoptical isomer forms (optically active substances, diastereomers and thelike). In addition, compounds having amido bond or double bond areincluded in the compound of the invention, so that tautomers andgeometrical isomers also exist. These isomers in the isolated or mixedform are included in the invention.

The compound of the invention forms a salt with an acid or a base.Examples of the salt with an acid include acid addition salts with inorganic acids such as mineral acids (e.g., hydrochloric acid,hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid,phosphoric acid and the like) or with organic acids (e.g., formic acid,acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid,fumaric acid, maleic acid, lactic acid, malic acid, citric acid,tartaric acid, carbonic acid, picric acid, methanesulfonic acid,ethanesulfonic acid, glutamic acid and the like).

Examples of the salt with a base include salts with inorganic bases suchas sodium, potassium, magnesium, calcium, aluminum and the like, withorganic bases such as methylamine, ethylamine, meglumine, ethanolamineand the like, or with basic amino acids such as lysine, arginine,ornithine and the like, as well as an ammonium salt. In addition, thecompound of the invention can form hydrates, solvates such as withethanol and the like and polymorphism.

In addition, a pharmacologically acceptable prodrug is included in thecompound of the invention. Examples of the group which forms thepharmacologically acceptable prodrug of the compound of the inventioninclude the groups described in Prog. Med., 5: 2157-2161 (1985) and thegroups described in “Development of Medicaments” vol. 7, MolecularDesigning, pp. 163-198, published in 1990 by Hirokawa Shoten.Illustratively, it is a group which can be converted into the primaryamine, secondary amine, OH, COOH or the like of the invention byhydrolysis or solvolysis or under a physiological condition, and itsexamples in the case of a prodrug of OH group include —OCO— (loweralkylene which may be substituted) —COOR (R represents H or a loweralkyl, the same shall apply hereinafter), —OCO— (lower alkenylene whichmay be substituted) —COOR, —OCO— (aryl which may be substituted), —OCO—(lower alkylene) —O— (lower alkylene) —COOR, —OCO—COR, —OCOO— (a loweralkyl which may have be substituted), —OSO₂— (a lower alkylene which besubstituted) —COOR, —O-phthalidyl,5-methyl-1,3-dioxolen-2-on-4-yl-methyloxy or the like.

Also, it is possible to use the compound of the invention in combinationwith an analgesic, an antiviral agent, a diabetes treating agent or thelike.

Examples of the analgesic include pirin, non-pirin and the likenon-steroidal anti-inflammatory drugs (NSAID), central analgesics(pentazocine and the like) and opioid analgesics (morphine and thelike).

Examples of the diabetes treating agent include sulfonylurea agents(tolbutamide and the like), α-glucosidase inhibitors (acarbose and thelike), thiazolidine-dione agents (triglytazone and the like) andbiguanide agents (metformin and the like).

Examples of the antiviral agent include acyclovir, paracyclovir,famciclovir and the like.

In addition to the above, the following can be exemplified as agentswhich can be jointly used.

Carbamazepine and the like anticonvulsants, imiplamine and the likeantidepressants, mexiletine and the like anti-arrhythmic drugs,lidocaine and the like local anesthetics, xanthine preparations(caffeine and the like), ergotamine agents and calcium antagonists(romelizin hydrochloride and the like).

Production Methods

In this specification, the signs used in the general production methods,reference examples, examples and tables have the following meanings.

DMF: dimethylformamide, DMSO: dimethyl sulfoxide, THF: tetrahydrofuran

Production Method 1: Reductive Amination

(In the formula, R^(a) means OH, or a lower alkyl-O—, or N(R⁴)(Alk₂)n—X—R³. Other signs are as defined in the foregoing. The sameshall apply hereinafter.)

From (II) to (I-a) is a usual reductive amination reaction. That is, thedesired (I-a) can be obtained by allowing an aldehyde (II) and acorresponding amine to undergo the reaction using a reducing agent(e.g., sodium triacetoxyborohydride, sodium cyanoborohydride, sodiumborohydride or the like) in a solvent (e.g., methylene chloride,1,2-dichloroethane, chloroform, THF, methanol, ethanol or the like), ifnecessary in the presence of an acid catalyst (e.g., acetic acid,hydrochloric acid or the like) or Lewis acid (e.g., titaniumtetraisopropoxide or the like). The (I-a) can also be synthesized byallowing the (II) and a corresponding amine to undergo the reaction inan inert solvent (e.g., toluene, benzene or the like) at a temperatureof from 10° C. to 150° C. under a dehydration reaction condition using adehydrating agent (e.g., Molecular Sieves or the like) or Dean-Starkfiltration equipment for dewatering as occasion demands, thereby formingan imine, and then treating it with a reducing agent (e.g., sodiumborohydride or the like) in a solvent (e.g., methanol, ethanol or thelike). In addition, the (I-a) can also be synthesized by using a metalcatalyst (e.g., palladium or the like) instead of the aforementionedreducing agent under a catalytic reduction condition, illustrativelyunder an atmosphere of hydrogen.

Production Method 2: Alkylation

(In the formula, A means a leaving group such as a halogen, sulfonyloxygroup or the like.)

From (III) to (I-a) is a usual N-alkylation reaction. That is, thedesired (I-a) can be obtained by allowing (III) and a correspondingamine to undergo the reaction at from ice-cooling to 200° C. in an inertsolvent (e.g., DMF, acetonitrile, chloroform, THF or the like) in thepresence of a base (e.g., potassium carbonate, sodium bicarbonate,triethylamine, ethyl diisopropylamine or the like). The correspondingamine may be used in excess amount in this reaction.

Production Method 3: Amidation

(In the formula, B means OH or N(R^(2′)) (Alk₁)m-R₁, wherein R^(2′)means H, a lower alkyl which may be substituted, or a general aminogroup protecting group.)

From (IV) to (I-b) is a usual amidation reaction. That is, the desired(I-b) can be obtained by activating a carboxylic acid (IV) with acondensing agent (e.g., dicyclohexylcarbodiimide,1-ethyl-3-(3-dimethylaminopropyl)carbodiimide,diphenylphosphoryltriazide, 1,1′-carbonyl-1H-imidazole,1-hydroxybenzotriazole or the like) in an inert solvent (e.g., DMF, THF,1,2-dichloroethane, chloroform or the like), and then allowing thisactive compound to react with a corresponding amine. For activating thecarboxylic acid, an acid chloride method in which thionyl chloride,oxalyl chloride or the like is used, a mixed acid anhydride method, oran active phosphoric acid ester method in which phosphorus oxychlorideor the like is used can also be used.

Production Method 4: N-Alkylation

From (I-c) to (I) is a usual N-alkylation reaction. That is, the desired(I) can be obtained by allowing to react with a corresponding alkylatingagent (e.g., alkyl halide, sulfonic acid alkyl ester or the like) underfrom ice-cooling to heating in an inert solvent (e.g., DMF, DMSO, THF,acetone, acetonitrile or the like) using a base (e.g., potassiumcarbonate, cesium carbonate, sodium hydride, potassium hydroxide or thelike).

General protecting groups and the like of hydroxyl group, amino group,ester group and the lie are described in detail in PROTECTIVE GROUPS INORGANIC SYNTHESIS, edited by THEODORA W. GREENE and PETER G. M. WUTS,and the disclosure of this reference is incorporated in thisspecification.

In this connection, the aforementioned production methods are notrestricted by the substituent groups of the formulae and can be broadlyapplied even to a case in which a compound of the invention has similarsubstituent groups or a case in which a reaction substrate and areactant have opposite relation.

The compound of the invention produced in this manner is isolated andpurified in its free form or as a salt thereof.

The isolation and purification are carried out by employing usualchemical operations such as extraction, concentration, evaporation,crystallization, filtration, recrystallization, various types ofchromatography and the like.

Various isomers can be separated by selecting appropriate materialcompounds or making use of the difference in physiological propertiesamong isomers. For example, optical isomers can be separated intostereochemically pure isomers by selecting an appropriate material or bya method for the optical resolution of racemic compounds (e.g., a methodin which they are converted into diastereomer salts with a generaloptically active base and then subjected to optical resolution).

A pharmaceutical preparation which contains one or more of the compoundsof the invention or salts thereof as the active ingredient is preparedusing carriers, fillers and other additives generally used in thepreparation of medicaments.

The carriers and fillers for pharmaceutical preparation use may beeither solid or liquid, and their examples include lactose, magnesiumstearate, starch, talc, gelatin, agar, pectin, acacia, olive oil, sesameoil, cacao butter, ethylene glycol and other generally used substances.

It may be administered either by oral administration through tablets,pills, capsules, granules, powders, solutions or the like, or byparenteral administration through injections such as for intravenousinjection, intramuscular injection or the like, suppositories,percutaneous preparations and the like. Its dose is optionally decidedby taking into consideration conditions of each case such as symptoms,age, sex and the like of the patient to be treated, but, usually, it isorally administered within the range of from 1 to 1,000 mg, preferablyfrom 50 to 200 mg, per day per adult by dividing the daily dose into 1to several doses per day or intravenously injected within the range offrom 1 to 500 mg per day per adult by dividing the daily dose into 1 toseveral doses per day, or continuously and intravenously injected withinthe range of from 1 to 24 hours per day. As a matter of course, sincethe dose varies under various conditions as described in the foregoing,a smaller dose than the above range may be sufficient enough in somecases.

As the solid composition for use in the oral administration according tothe invention, tablets, powders, granules and the like are used. In sucha solid composition, one or more active substances are mixed with atleast one inert diluent such as lactose, mannitol, glucose,hydroxypropylcellulose, microcrystalline cellulose, starch, polyvinylpyrrolidone or aluminum magnesium metasilicate. In accordance with theusual way, the composition may contain other additives than the inertdiluent, which include a lubricant such as magnesium stearate, adisintegrating agent such as starch or calcium cellulose glycolate, astabilizing agent such as lactose and a solubilization assisting agentsuch as glutamic acid or aspartic acid. As occasion demands, tablets orpills may be coated with a film of a gastric or enteric substance suchas sucrose, gelatin, hydroxypropylcellulose,hydroxypropylmethylcellulose phthalate or the like.

The liquid composition for oral administration use includespharmaceutically acceptable emulsions, solutions, suspensions, syrups,elixirs and the like and contains a generally used inert diluent such aspurified water or ethanol. In addition to the inert diluent, thiscomposition may also contain auxiliary agents such as a moistening agentand a suspending agent, as well as a sweetener, a flavor, an aromaticand an antiseptic.

The injections for parenteral administration use include aseptic aqueousor non-aqueous solutions, suspensions and emulsions. Examples of thediluent for use in the aqueous solutions and suspensions includedistilled water for injection and physiological saline. Examples of thediluent for use in the non-aqueous solutions and suspensions includepropylene glycol, polyethylene glycol, plant oils (e.g., olive oil),alcohols (e.g., ethanol) and polysorbate 80. Such a composition mayfurther contain auxiliary agents such as an antiseptic, a moisteningagent, an emulsifying agent, a dispersing agent, a stabilizing agent(e.g., lactose) and a solubilization assisting agent (e.g., glutamicacid or aspartic acid). They are sterilized by, for example, filtrationthrough a bacteria retaining filter, blending of a germicide orirradiation. Alternatively, they may be used by firstly making intosterile solid compositions and dissolving them in sterile water or asterile solvent for injection prior to their use.

EXAMPLES

Next, the invention is described further in detail based on examples,but the invention is not limited to these examples. In this connection,methods for producing material compounds used in the Examples aredescribed as reference examples. (The abbreviations used in thefollowing are the same as those used in the production methods.)

¹H-NMR; ¹H-Nuclear magnetic resonance spectrum (This was measured at 300MHz or 400 MHz, using DMSO-d₆ or deuterium chloroform (to be referred toas CDCl₃ hereinafter) as the measuring solvent and tetramethylsilane asthe internal standard, and the chemical shift was shown by ppm. br;broad, s; singlet, d; doublet, t; triplet, q; quartet, m; multiplet)

MS; Mass spectrometry (FAB+: cation fast atom bombardment massspectrometry, M: molecular weight)

Ex; Example number

Salt; Salt

Data; Physicochemical properties (mass spectrometry)

Silica gel was used as the filler in the column chromatography used inthe purification.

Reference Example 16-Hydroxymethyl-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide

In an ice bath, 1-hydroxybenzotriazole (2.03 g) and1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (5.75 g)were added to a DMF (25 ml) suspension of6-hydroxymethylthiazolo[3,2-a]benzimidazole-2-carboxylic acid (2.48 g),and the reaction mixture was stirred for 30 minutes in the ice bath andthen for 2 hours by removing the ice bath. Methylneopentylaminehydrochloride (2.75 g) and triethylamine (2.8 ml) were added to thereaction mixture, and the resulting reaction mixture was stirred at thesame temperature for 2 hours. After completion of the reaction, thereaction mixture was poured into 1 M sodium hydroxide aqueous solution(50 ml). The insoluble matter was collected by filtration, washed withwater (150 ml) and then dried by heating under a reduced pressure toobtain the pale yellow title compound (1.98 g).

¹H-NMR (DMSO-d₆); 0.96 (s, 9H), 3.41 (br, 2H), 3.46 (br, 3H), 4.67 (d,2H), 5.33 (t, 1H), 7.31 (d, 1H), 7.62 (d, 2H), 8.10 (s, 1H), 9.09 (s,1H)

Reference Example 26-Formyl-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide

Triethylamine (5.58 ml) and sulfur trioxide-pyridine mixture (7.96 g)were added to a DMSO (50 ml) solution of the compound of ReferenceExample 1 (3.31 g). The reaction mixture was stirred for 6 hoursaccompanied by exothermic reaction. After completion of the reaction,the reaction mixture was carefully added to sodium bicarbonate aqueoussolution. The insoluble matter was collected by filtration, washed withwater (500 ml) and then dried by heating under a reduced pressure toobtain the pale ivory-colored title compound (3.21 g).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 3.42 (br, 2H), 3.48 (br, 3H), 7.85 (d,1H), 7.95 (dd, 1H), 8.69 (d, 1H), 9.22 (s, 1H), 10.09 (s, 1H)

Reference Example 36-Chloromethyl-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamideHydrochloride

DMF (one drop) was added to a thionyl chloride (5 ml) solution of thecompound of Reference Example 1 (994 mg). The reaction mixture wasstirred for 30 minutes accompanied by exothermic reaction and foaming.After completion of the reaction, the reaction mixture was diluted withtoluene (40 ml). The precipitate was collected by filtration, washedwith toluene and then dried by heating under a reduced pressure toobtain the title compound (1,105 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 3.42 (br, 2H), 3.48 (br, 3H), 4.98 (s,2H), 7.51(d, 1H), 7.74 (d, 1H), 8.27 (s, 1H), 9.20 (s, 1H)

Reference Example 4 Ethyl6-formylthiazolo[3,2-a]benzimidazole-2-carboxylate

Triethylamine (39.02 ml) and sulfur trioxide-pyridine mixture (55.71 g)were added to a DMSO (300 ml) solution of ethyl6-hydroxymethylthiazolo[3,2-a]benzimidazole-2-carboxylate (19.34 g). Thereaction mixture was stirred for 2 hours accompanied by exothermicreaction. After completion of the reaction, the reaction mixture wascarefully added to saturated sodium bicarbonate aqueous solution. Theinsoluble matter was collected by filtration, washed with water and thendried by heating under a reduced pressure to obtain the paleivory-colored title compound (19.10 g).

¹H-NMR (DMSO-d₆); 1.36 (t, 3H), 4.39 (q, 2H), 7.87 (d, 1H), 7.97 (dd,1H), 8.76 (d, 1H), 9.51 (s, 1H), 10.08 (s, 1H)

Reference Example 5 Ethyl6-({[((R)-tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxylate

(R)-Tetrahydrofurfurylamine (3.1 ml) was added to a dichloroethane (200ml) solution of the compound of Reference Example 4 (5.49 g), andstirred at room temperature for 1 hour. Sodium triacetoxyborohydride(8.48 g) was added to the reaction mixture and stirred at the roomtemperature for a whole day and night. After completion of the reaction,the reaction mixture was mixed with saturated sodium bicarbonate aqueoussolution and extracted with chloroform. The organic layer was collected,washed with saturated sodium bicarbonate aqueous solution, water andsaturated brine and then dried with anhydrous magnesium sulfate andconcentrated under a reduced pressure. The residue was purified by acolumn chromatography (eluent; ethyl acetate, then ethyl acetatemethanol=95:5 and further chloroform:methanol=10:1) to obtain the titlecompound (6.10 g).

¹H-NMR (CDCl₃); 1.42 (t, 3H), 1.52-1.61 (m, 1H), 1.85-2.02 (m, 3H), 2.68(dd, 1H), 2.75 (dd, 1H), 3.72-3.79 (m, 1H), 3.82-3.88 (m, 1H), 4.00 (s,2H), 4.02-4.09 (m, 1H), 4.42 (q, 2H), 7.37 (dd, 1H), 7.72 (d, 1H), 7.75(d, 1H), 8.41 (s, 1H)

Reference Example 6 Ethyl6-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxylate

A chloroform (30 ml) solution of di-tert-butyl dicarbonate (3.71 g) wasadded to a chloroform (60 ml) solution of the compound of ReferenceExample 5 (6.10 g) and stirred at room temperature for 2 hours. Aftercompletion of the reaction, the reaction mixture was concentrated undera reduced pressure to obtain the light brown title compound (7.74 g).

¹H-NMR (CDCl₃); 1.43 (t, 3H), 1.36-1.57 (m, 9H), 1.81-2.02 (m, 3H),3.02-3.22 (m, 1H), 3.28-3.65 (m, 1H), 3.73-3.80 (m, 1H), 3.81-3.91 (m,1H), 4.01-4.18 (m, 1H), 4.43 (t, 2H), 4.64 (d, 1H), 4.84 (d. 1H), 7.33(br, 1H), 7.61 (br, 1H), 7.73 (d, 1H), 8.41 (s, 1H)

Reference Example 76-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxylicacid

A methanol (100 ml) suspension of the compound of Reference Example 6(7.74 g) was mixed with 1 M sodium hydroxide aqueous solution (40 ml)and stirred at room temperature for 2 hours. After completion of thereaction, the reaction mixture was mixed with 1 M hydrochloric acidaqueous solution (40 ml). The precipitate was collected by filtration,washed with water and then dried by heating under a reduced pressure toobtain the colorless title compound (6.57 g).

¹H-NMR (DMSO-d₆); 1.37 (br, 3H), 1.45 (br, 6H), 1.73-1.93 (m, 3H),3.06-3.48 (m, 3H), 3.65 (dd, 1H), 3.77 (dd, 1H), 3.98-4.07 (m, 1H), 4.55(d, 1H), 4.69 (d, 1H), 7.27 (dd, 1H), 7.67 (d, 1H), 8.01 (d, 1H), 9.31(s, 1H), 13.84 (br, 1H)

Reference Example 86-Hydroxymethyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide

1-Hydroxybenzotriazole (10.1 g) and1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (28.8 g)were added to a DMF (500 ml) suspension of6-hydroxymethylthiazolo[3,2-a]benzimidazole-2-carboxylic acid (12.4 g),and the reaction mixture was stirred at room temperature for 2 hours.Neopentylamine (17.7 ml) was added to the reaction mixture, and theresulting reaction mixture was stirred at the same temperature for 2hours. After completion of the reaction, the reaction mixture was pouredinto 0.5 M sodium hydroxide aqueous solution (2 l). The insoluble matterwas collected by filtration, washed with water and then with a mixedsolvent of hexane and diethyl ether (mixing ratio; 3:1) and then driedby heating under a reduced pressure to obtain the title compound (12.0g).

¹H-NMR (DMSO-d₆); 0.94 (s, 9H), 3.13 (d, 2H), 4.68 (d, 2H), 5.33 (t,1H), 7.33 (d, 1H), 7.65 (d, 2H), 7.88 (br, 1H), 8.52 (t, 1H), 9.14 (s,1H)

Reference Example 96-Formyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide

Triethylamine (21.1 ml) was added to a DMSO (200 ml) solution of thecompound of Reference Example 8 (12.0 g), and then a sulfurtrioxide-pyridine mixture (30.0 g) was gradually added thereto at roomtemperature. After completion of the addition, the reaction mixture wasstirred at room temperature for 1.5 hours. After completion of thereaction, the reaction mixture was added to 0.1 M sodium hydroxideaqueous solution (2 l). The precipitate was collected by filtration,washed with water and diethyl ether in that order and then dried byheating under a reduced pressure to obtain the title compound (10.3 g).

¹H-NMR (DMSO-d₆); 0.94 (s, 9H), 3.14 (d, 2H), 7.87 (d, 1H), 7.96 (d,2H), 8.52 (br, 1H), 8.67 (t, 1H), 9.25 (s, 1H), 10.11 (s, 1H)

Reference Example 10N-(1,3-Dioxolan-2-ylmethyl)-6-hydroxymethyl-N-methylthiazolo[3,2-a]benzimidazole-2-carboxamide

1-Hydroxybenzotriazole (10.1 g) and1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (28.8 g)were added to a DMF (500 ml) suspension of6-hydroxymethylthiazolo[3,2-a]benzimidazole-2-carboxylic acid (12.4 g),and the reaction mixture was stirred at room temperature for 1.5 hours.N-(1,3-Dioxolan-2-ylmethyl)-N-methylamine (17.1 ml) was added to thereaction mixture, and the resulting reaction mixture was stirred at thesame temperature for 1 hour. After completion of the reaction, thereaction mixture was poured into 0.5 M sodium hydroxide aqueous solution(2 l). The insoluble matter was collected by filtration, washed withwater and then with a mixed solvent of hexane and diethyl ether (mixingratio; 3:1) and then dried by heating under a reduced pressure to obtainthe title compound (8.62 g).

¹H-NMR (DMSO-d₆); 3.07-3.98 (m, 9H), 4.67 (d, 2H), 5.08 (br, 1H), 5.32(t, 1H), 7.31 (d, 1H), 7.62 (d, 1H), 8.09 (br, 1H), 9.04 (br, 1H)

Reference Example 11N-(1,3-Dioxolan-2-ylmethyl)-6-formyl-N-methylthiazolo[3,2-a]benzimidazole-2-carboxamide

Triethylamine (13.8 ml) was added to a DMSO (180 ml) solution of thecompound of Reference Example 10 (8.6 g), and then a sulfurtrioxide-pyridine mixture (19.7 g) was gradually added thereto at roomtemperature. After completion of the addition, the reaction mixture wasstirred at room temperature for 1.5 hours. After completion of thereaction, the reaction mixture was added to 0.07 M sodium hydroxideaqueous solution (2.15 l). The precipitate was collected by filtration,washed with water and diethyl ether in that order and then dried byheating under a reduced pressure to obtain the title compound (4.41 g).

¹H-NMR (DMSO-d₆); 3.30-3.98 (m, 9H), 5.09 (br, 1H), 7.86 (d, 1H), 7.96(d, 1H), 8.71 (br, 1H), 9.20 (br, 1H), 10.01 (s, 1H)

Reference Example 12 (4-Methoxytetrahydropyran-4-yl)methylamine

Under ice-cooling, a diethyl ether (5 ml) solution of4-cyano-4-methoxytetrahydropyran (600 mg; Chemistry Letters, pp.937-940, 1984) was added dropwise to a diethyl ether (10 ml) suspensionof lithium aluminum hydride (242 mg) spending 20 minutes and, aftercompletion of the dropwise addition, stirred at room temperature for 4hours. After completion of the reaction, the reaction mixture wasice-cooled, and sodium sulfate decahydrate was gradually added to thereaction mixture until foaming stopped. After completion of theaddition, the insoluble matter was filtered, and the filtered solid waswashed with diethyl ether. The filtrate and washed solution werecombined and concentrated under a reduced pressure to obtain the titlecompound (597 mg).

¹H-NMR (DMSO-d₆); 1.17 (br, 2H), 1.40-1.47 (m, 2H), 1.57-1.62 (m, 2H),2.53 (br, 2H), 3.07 (s, 3H), 3.47-3.66 (m, 4H)

Reference Example 13 2-(tert-Butoxycarbonyl)aminomethyl-1,3-dithiolan

At room temperature, di-tert-butyl dicarbonate (1.69 g) was added to anethyl acetate (15 ml) solution of 1,3-dithiolan-2-ylmethylamine (1.0 g)and stirred at room temperature for a whole day and night. Aftercompletion of the reaction, the reaction mixture was separated using amixed solution of ethyl acetate and water. The organic layer was washedwith water and saturated brine, dried with anhydrous sodium sulfate andthen concentrated under a reduced pressure to obtain the title compound(1.85 g).

¹H-NMR (DMSO-d₆); 1.38 (s, 9H), 3.10 (t, 2H), 3.18 (br, 4H), 4.49 (t,1H), 7.11 (br, 1H)

Reference Example 14 2-Methylaminomethyl-1,3-dithiolan

Under ice-cooling, a tetrahydrofuran (20 ml) solution of the compound ofReference Example 13 (1.85 g) was added dropwise to a tetrahydrofuran(20 ml) suspension of lithium aluminum hydride (597 mg) spending 20minutes and, after completion of the dropwise addition, heated underreflux for a whole day and night. After completion of the reaction, thereaction mixture was ice-cooled, and sodium sulfate decahydrate wasgradually added to the reaction mixture until foaming stopped. Aftercompletion of the addition, the insoluble matter was filtered, and thefiltered solid was washed with diethyl ether. The filtrate and washedsolution were combined, concentrated under a reduced pressure and thendried by heating under a reduced pressure to obtain the title compound(782 mg).

¹H-NMR (DMSO-d₆); 1.75 (br, 1H), 2.28 (d, 3H), 2.67 (dd, 2H), 3.14-3.19(m, 4H), 4.55 (t, 1H)

Reference Example 15N-Methyl-6-[(2-morpholin-4-ylethoxy)methyl]-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

In an ice bath, sodium hydride (68 mg) was added to a DMF (10 ml)suspension of the compound of Reference Example 3 (566 mg) and stirredin the ice bath for 5 minutes (reaction mixture 1). Also, in an icebath, sodium hydride (68 mg) was added to a DMF (10 ml) solution of2-morpholin-4-ylethanol (0.178 ml) and stirred in the ice bath for 35minutes (reaction mixture 2). In an ice bath, the reaction mixture 2 wasadded dropwise to the reaction mixture 1 and, after warming up to roomtemperature, sodium hydride (51 mg) was gradually added thereto andstirred at room temperature for a whole day and night. After completionof the reaction, the reaction mixture was poured into saturated sodiumbicarbonate aqueous solution and extracted with ethyl acetate. Theorganic layer was washed with water and saturated brine, dried withanhydrous sodium sulfate and then concentrated under a reduced pressure.The resulting residue was purified by a column chromatography (eluent;chloroform, then chloroform methanol=90:10 and thenchloroform:methanol=85:15). The formed product was made intohydrochloride in the usual way, and the thus crystallized residue wasrecrystallized from ethanol and ethyl acetate to obtain the titlecompound (92 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 3.09-3.18 (m, 2H), 3.38-3.49 (m, 9H),3.85-3.96 (m, 6H), 4.72 (s, 2H), 7.41 (dd, 1H), 7.72 (d, 1H), 8.35 (br,1H), 9.27(s, 1H), 11.19 (br, 1H)

Example 5N-Methyl-6-methoxybutylaminomethyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A THF (10 ml) solution of the compound of Example 4 (304 mg) was mixedwith di-tert-butyl dicarbonate (166 mg) and stirred at room temperaturefor 1 hour. After completion of the reaction, the reaction mixture wasconcentrated under a reduced pressure, and the thus obtained residue waspurified by a column chromatography (eluent; hexane:ethylacetate=50:50-0:100) to obtainN-methyl-6-[(N-tert-butoxycarbonyl)-4-hydroxybutyl]aminomethyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide(380 mg). In an ice bath, methyl iodide (71 μl) and sodium hydride (36mg) were added to a DMF (5 ml) solution of this compound (380 mg) andstirred in the ice bath for 1 hour. Methyl iodide (213 μl) was furtheradded to the reaction mixture and stirred at room temperature for awhole day and night. After completion of the reaction, the reactionmixture was mixed with saturated sodium bicarbonate aqueous solution andextracted with ethyl acetate. The organic layer was collected, washedwith water and saturated brine, dried with anhydrous magnesium sulfateand then concentrated under a reduced pressure. The thus obtainedresidue was purified by a column chromatography (eluent; hexane:ethylacetate=70:30-10:90) to obtainN-methyl-6-[(N-tert-butoxycarbonyl)-6-methoxybutyl]aminomethyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide(50 mg). In an ice bath, 4 M hydrochloric acid-ethyl acetate solution (6ml) was added to an ethyl acetate (2 ml) solution of this compound (50mg) and then stirred for 1 hour by removing the ice bath. Aftercompletion of the reaction, the reaction mixture was dissolved inethanol and then concentrated under a reduced pressure. The resultingresidue was washed with a mixed solvent of hot ethanol-ethyl acetate toobtain the title compound (40 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 1H), 1.50-1.58 (m, 2H), 1.67-1.77 (m, 2H),2.91 (br, 2H), 3.31 (t, 1H), 3.42 (br, 2H), 3.48 (br, 3H), 4.22-4.28 (m,2H), 6.52 (br, 2H), 7.69 (dd, 1H), 7.79 (d, 1H), 8.25 (s, 1H), 9.16 (s,1H), 9.44 (br, 2H)

MS (FAB+); 417 (M+1)

Example 6N-Methyl-N-neopentyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide1.5 Fumarate

A DMF (40 ml) solution of the compound of Reference Example 3 (386 mg)was mixed with oxetan-3-ylamine hydrochloride (548 mg), potassiumcarbonate (691 mg) and triethylamine (0.67 ml), and the mixture wasstirred in an oil bath of 50° C. for a whole day and night. Aftercompletion of the reaction, the reaction mixture was poured into a mixedsolution of ethyl acetate and water. The insoluble matter was filtered,and the resulting water layer was extracted with ethyl acetate. Theorganic layer was collected, washed with water and saturated brine,dried with anhydrous magnesium sulfate and then concentrated under areduced pressure. The thus obtained residue was purified by a fractionalthin layer chromatography (eluent; chloroform:methanol=9:1). The thusformed product was made into fumarate in the usual way andrecrystallized from ethanol and ethyl acetate to obtain the titlecompound (65 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 3.42 (br, 2H), 3.47 (br, 3H), 3.84 (s,2H), 3.93-4.01 (m, 1H), 4.35 (t, 2H), 4.59 (t, 2H), 6.62 (s, 3H), 7.34(dd, 1H), 7.62 (d, 1H), 8.07 (br, 1H), 9.06 (s, 1H)

MS (FAB+); 387 (M+1)

The compounds of Examples 8, 9, 16 and 19 were synthesized by the samemethod of Example 6.

Example 6 (Another Method)N-Methyl-N-neopentyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide1.5 Fumarate

A dichloroethane (10 ml) solution of the compound of Reference Example 2(329 mg) was mixed with oxetan-3-ylamine hydrochloride (329 mg),triethylamine (418 μl) and acetic acid (171 μl), and the mixture wasstirred at room temperature for 2 hours. The reaction mixture was mixedwith sodium triacetoxyborohydride (1,060 mg) and further stirred at roomtemperature for 22 hours. After completion of the reaction, the reactionmixture was mixed with water and 1 M sodium hydroxide aqueous solutionand extracted with 5% methanol-containing chloroform. The organic layerwas collected, washed with saturated brine, dried with anhydrousmagnesium sulfate and then concentrated under a reduced pressure. Theresulting residue was purified by a column chromatography (eluent;chloroform:methanol=100:0-100:10) to obtainN-methyl-N-neopentyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide(343 mg). The thus obtained compound was dissolved in ethanol and mixedwith fumaric acid (165 mg), and then the mixture was concentrated undera reduced pressure. By recrystallizing the thus obtained residue fromethanol and ethyl acetate, the title compound (298 mg) was obtained.

Example 7N-Methyl-6-({[(3-methyloxetan-3-yl)methyl]amino}methyl)-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide

A DMF (10 ml) solution of the compound of Reference Example 3 (1.62 g)was mixed with potassium phthalimide (2.31 g) and potassium carbonate(2.87), and the mixture was stirred at room temperature for 14 hours.After completion of the reaction, the reaction mixture was poured intowater (100 ml) and stirred at room temperature for 30 minutes. Theprecipitate was collected by filtration, washed with water and then witha mixed solvent of hexane and diethyl ether (mixing ratio; 3:1) anddried by heating under a reduced pressure to obtainN-methyl-N-neopentyl-6-[(phthalimide)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide(1.76 g). Under ice-cooling, 40% methylamine-methanol solution (2.4 ml)was added dropwise to a methanol (20 ml) solution of this compound (1.75g) and, after completion of the dropwise addition, this was heated underreflux for 1 hour. After completion of the reaction, the reactionmixture was concentrated under a reduced pressure, and the resultingresidue was purified by a column chromatography (eluent;chloroform:methanol: 29% aqueous ammonia=100:0:0-93:7:0.7-90:10:1) toobtain6-aminomethyl-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide(702 mg). A methanol (30 ml) solution of this compound (524 mg) wasmixed with (3-methyloxetan-3-yl)methyl methanesulfonate (286 mg) andsodium carbonate (496 mg) and stirred in an oil bath of 100° C. for 6days. After completion of the reaction, the reaction mixture was mixedwith water and extracted with ethyl acetate. The organic layer waswashed with water and saturated brine, dried with anhydrous sodiumsulfate and then concentrated under a reduced pressure. Byrecrystallizing the resulting residue from hexane and ethyl acetate, thetitle compound (316 mg) was obtained.

¹H-NMR (DMSO-d₆); 0.96 (s, 9H), 1.25 (s, 3H), 2.27 (br, 1H), 2.67 (br,2H), 3.41 (br, 2H), 3.47 (br, 3H), 3.88 (br, 2H), 4.17 (d, 2H), 4.34 (d,2H), 7.39 (dd, 1H) 7.63 (d, 1H), 8.05 (s, 1H), 9.05 (s, 1H)

MS (FAB+); 415 (M+1)

Example 10N-Methyl-N-neopentyl-6-({[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (5 ml) solution of the compound of Reference Example 3 (386 mg)was mixed with potassium carbonate (691 mg) and(R)-tetrahydrofurfurylamine (506 mg), and the mixture was stirred atroom temperature for 3 hours. After completion of the reaction, thereaction mixture was poured into a mixed solution of ethyl acetate andwater. The insoluble matter was filtered and the water layer wasextracted with ethyl acetate. The organic layers were collected, washedwith water and saturated brine, dried with anhydrous magnesium sulfateand then concentrated under a reduced pressure. The resulting residuewas purified by a column chromatography (eluent; ethyl acetate and thenchloroform:methanol=10:1). The thus formed product was made intohydrochloride in the usual way and then recrystallized from ethanol andethyl acetate to obtain the title compound (192 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 1.52-1.62 (m, 1H), 1.77-1.89 (m, 2H),1.95-2.05 (m, 1H), 2.80-2.92 (m, 1H), 2.98-3.08 (m, 1H), 3.42 (br, 2H),3.48 (br, 3H), 3.71 (dd, 1H), 3.80 (dd, 1H), 4.17-4.36 (m, 3H), 7.69 (d,1H), 7.79 (d, 1H), 8.27 (s, 1H), 9.18 (s, 1H), 9.34 (br, 1H), 9.68 (br,1H)

MS (FAB+); 415 (M+1)

Example 11N-Methyl-N-neopentyl-6-({[((S)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamideDihydrochloride

A DMF (12 ml) solution of the compound of Reference Example 3 (340 mg)was mixed with (S)-tetrahydrofurfurylamine (492 mg) and potassiumcarbonate (672 mg), and the mixture was stirred in an oil bath of 50° C.for 13 hours. After completion of the reaction, the reaction mixture wasmixed with water and extracted with ethyl acetate. The insoluble matterwas filtered, and the water layer was extracted with ethyl acetate. Theorganic layers were washed with water and then extracted with 1 Mhydrochloric acid aqueous solution. The water layer was washed withchloroform, and then the water layer was adjusted to basic (pH 9-11)with saturated sodium bicarbonate aqueous solution and extracted withchloroform. The organic layer was dried with anhydrous sodium sulfateand concentrated under a reduced pressure. The product was made intohydrochloride in the usual way and recrystallized from 2-propanol toobtain the title compound (165 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 1.51-1.60(m, 1H), 1.79-1.86 (m, 2H),1.96-2.04 (m, 1H), 2.86-2.91 (m, 1H), 3.04-3.07 (m, 1H), 3.42 (br, 2H),3.47 (br, 3H), 3.72 (dd, 1H), 3.80 (dd, 1H), 4.19-4.31 (m, 3H), 7.62 (d,1H), 7.78 (d, 1H), 8.20 (s, 1H), 9.10 (s, 1H), 9.20-9.46 (m, 2H)

MS (FAB+); 415 (M+1)

Example 126-{[(1,3-Dioxolan-2-ylmethyl)amino]methyl}-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (12 ml) solution of the compound of Reference Example 3 (340 mg)was mixed with 1,3-dioxolan-2-ylmethylamine (167 mg) and potassiumcarbonate (672 mg), and the mixture was stirred in an oil bath of 50° C.for 12.5 hours. After completion of the reaction, the reaction mixturewas mixed with water and extracted with ethyl acetate. The insolublematter was filtered, and the water layer was extracted with ethylacetate. The organic layer was washed with water and then extracted with1 M hydrochloric acid aqueous solution. The water layer was washed withchloroform, and then the water layer was adjusted to basic (pH 9-11)with saturated sodium bicarbonate aqueous solution and extracted withchloroform. The organic layer was dried with anhydrous sodium sulfateand then concentrated under a reduced pressure. The resulting productwas made into hydrochloride in the usual way and recrystallized from2-propanol to obtain the title compound (104 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 3.12-3.13 (m, 2H), 3.42 (br, 2H), 3,47(br, 3H), 3.85-3.93 (m, 2H), 3.96-4.04 (m, 2H), 4.33 (br, 2H), 5.19 (t,1H), 7.59 (dd, 1H), 7.77 (d, 1H), 8.19 (s, 1H), 9.08 (s, 1H), 9.30 (br,1H), 9.37 (br, 1H)

MS (FAB+); 417 (M+1)

Example 12 (Another Method)

A dichloroethane (40 ml) solution of the compound of Reference Example 2(1,364 mg) was mixed with 1,3-dioxolan-2-ylmethylamine (1,281 mg) andacetic acid (711 μl), and the mixture was stirred at room temperaturefor 2 hours. The reaction mixture was mixed with sodiumtriacetoxyborohydride (4,387 mg) and further stirred at room temperaturefor 20 hours. After completion of the reaction, the reaction mixture wasmixed with 1 M sodium hydroxide aqueous solution and extracted with 5%methanol-containing chloroform. The organic layer was collected, washedwith saturated brine, dried with anhydrous magnesium sulfate and thenconcentrated under a reduced pressure. The resulting residue waspurified by a column chromatography (eluent; chloroform:methanol=95:5)to obtain6-{[(1,3-Dioxolan-2-ylmethyl)amino]methyl}-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide(1,564 mg). The thus obtained compound was dissolved in ethanol andmixed with 1 M hydrochloric acid aqueous solution, and then the mixturewas concentrated under a reduced pressure. By recrystallizing the thusobtained residue from ethanol and ethyl acetate, the title compound(1,410 mg) was obtained.

Example 13N-Methyl-N-neopentyl-6-({methyl[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamideDihydrochloride

Under ice cooling, a DMF (20 ml) solution of the compound of Example 24(448 mg) was mixed with methyl iodide (146 μl) and sodium hydride (88mg), and the mixture was stirred under ice-cooling for 2.5 hours. Aftercompletion of the reaction, the reaction mixture was poured intosaturated sodium bicarbonate aqueous solution and extracted with ethylacetate. The organic layer was washed with water and saturated brine,dried with anhydrous sodium sulfate and then concentrated under areduced pressure. The resulting residue was purified by a columnchromatography (eluent; chloroform, then chloroform:methanol=90:10 andthen chloroform:methanol=85:15). The thus obtained product was made intohydrochloride in the usual way and recrystallized from ethanol and ethylacetate to obtain the title compound (140 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 1.48-1.55 (m, 1H), 1.79-1.86 (m, 2H),2.01-2.07 (m, 1H), 2.74-2.75 (m, 3H), 3.03-3.37 (m, 2H), 3.42 (brs, 2H),3.49 (brs, 3H), 3.71-3.86 (m, 2H), 4.39-4.47 (m, 2H), 4.53-4.63 (m, 1H),7.72 (ddd, 1H), 7.81 (d, 1H), 8.36 (d, 1H), 9.22 (s, 1H), 10.67 (br,1H), 11.06 (br, 1H)

MS (FAB+); 429 (M+1)

Example 15N-Methyl-N-neopentyl-6-{[(tetrahydro-2H-pyran-4-yl)amino]methyl}thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (12 ml) solution of the compound of Reference Example 3 (340 mg)was mixed with tetrahydropyran-4-ylamine hydrochloride (367 mg) andpotassium carbonate (672 mg), and the mixture was stirred in an oil bathof 50° C. for 36 hours. After completion of the reaction, the reactionmixture was mixed with water and extracted with ethyl acetate. Theinsoluble matter was filtered, and the water layer was extracted withethyl acetate. The organic layer was washed with water and thenextracted with 1 M hydrochloric acid aqueous solution. The water layerwas washed with chloroform, and then the water layer was adjusted tobasic (pH 9-11) with saturated sodium bicarbonate aqueous solution andextracted with chloroform. The organic layer was dried with anhydroussodium sulfate and then concentrated under a reduced pressure. Theresulting product was made into hydrochloride in the usual way andrecrystallized from ethanol to obtain the title compound (77 mg).

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 1.71 (ddd, 2H), 2.06-2.12 (m, 2H),3.27-3.38 (m, 3H), 3.43 (br, 2H), 3.47 (br, 3H), 3.94 (dd, 2H),4.28-4.32 (m, 2H), 7.66 (d, 1H), 7.79 (d, 1H), 8.24 (s, 1H), 9.11 (s,1H), 9.32-9.54 (m, 2H)

MS (FAB+); 415 (M+1)

Example 17N-Methyl-N-neopentyl-6-({[(tetrahydro-2H-pyran-4-yl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (10 ml) solution of the compound of Reference Example 2(230 mg) was mixed with acetic acid (208 μl) and(tetrahydropyran-4-yl)methylamine (252 mg), and the mixture was stirredat room temperature for 1.5 hours. The reaction mixture was mixed withsodium triacetoxyborohydride (278 mg) and further stirred at roomtemperature for 1.5 hours. After completion of the reaction, thereaction solution was adjusted to acidic (pH 1-3) by adding 1 Mhydrochloric acid aqueous solution (30 ml) and then extracted with 1 Mhydrochloric acid aqueous solution and washed with chloroform. The waterlayer was adjusted to basic (pH 11-13) by adding 3 M sodium hydroxideaqueous solution (30 ml) and then extracted with chloroform. The organiclayer was dried with anhydrous sodium sulfate and concentrated under areduced pressure. The resulting residue was purified by a columnchromatography (eluent; chloroform:methanol: 29% aqueousammonia=100:0:0-93:7:0.7-90:10:1). By making the product intohydrochloride in the usual way and recrystallizing it from ethanol andethyl acetate, the title compound (220 mg) was obtained.

¹H-NMR (DMSO-d₆); 0.97 (s, 9H), 1.14-1.26 (m, 2H), 1.67-1.75 (m, 2H),1.97-2.10 (m, 1H), 2.76-2.83 (m, 2H), 3.26 (dt, 2H), 3.42 (br, 2H), 3.48(br, 3H), 3.83 (dd, 2H), 4.23-4.32 (m, 2H), 7.76 (d, 1H), 7.80 (d, 1H),8.31 (s, 1H), 9.21 (s, 1H), 9.48-9.70 (m, 2H)

MS (FAB+); 429 (M+1)

The compounds of Examples 14 and 18 were synthesized by the same methodof Example 17.

Example 23(R)-N-Neopentyl-6-{[(tetrahydro-3-furyl)amino]methyl}thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example 9(400 mg) was mixed with acetic acid (362 μl),(R)-(tetrahydrofuran-3-yl)amine p-toluenesulfonate (988 mg) andtriethylamine (530 μl), and the mixture was stirred at room temperaturefor 1 hour. Subsequently, this was mixed with sodiumtriacetoxyborohydride (485 mg) and further stirred at room temperaturefor 2 hours. After completion of the reaction, the reaction mixture wasmixed with saturated sodium bicarbonate aqueous solution and stirred,and then the insoluble matter was filtered and washed with chloroform.The filtrate and washing solution were combined and concentrated under areduced pressure, and the resulting residue was purified by a columnchromatography (eluent; chloroform:methanol: 29% aqueousammonia=100:0:0-93:7:0.7-90:10:1). The thus obtained product wasextracted with chloroform, washed with 1 M sodium hydroxide aqueoussolution and saturated brine, and then the organic layer was dried withanhydrous sodium sulfate and concentrated under a reduced pressure. Bymaking the product into hydrochloride in the usual way and washing itwith a mixed solvent of ethanol and ethyl acetate, the title compound(346 mg) was obtained.

¹H-NMR (DMSO-d₆); 0.92 (s, 9H), 2.09-2.25 (m, 2H), 3.12 (d, 2H), 3.66(dd, 1H), 3.74-3.85 (m, 2H), 3.81-3.98 (m, 2H), 4.25-4.40 (m, 2H), 7.68(d, 1H), 7.78 (d, 1H), 8.20 (s, 1H), 9.08 (t, 1H), 9.44 (s, 1H), 9.92(br, 2H)

MS (FAB+); 387 (M+1)

The compounds of Examples 1, 2, 3, 4, 20, 21, 22, 25, 27, 29, 32 and 81were synthesized by the same method of Example 23.

Example 24(R)-N-Neopentyl-6-({[(tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (70 ml) solution of the compound of Reference Example 7 (3.10 g)was mixed with 1-hydroxybenzotriazole (1.42 g) and1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (4.03 g),and the mixture was stirred at room temperature for 2 hours. Thereaction mixture was mixed with neopentylamine (2.47 ml) and furtherstirred at room temperature for 2 hours. After completion of thereaction, the reaction mixture was separated between layers using amixture of water and ethyl acetate, and the water layer was extractedwith ethyl acetate. The organic layer was collected, washed with 5%citric acid aqueous solution, water, 1 M sodium hydroxide aqueoussolution, water and saturated brine, dried with anhydrous magnesiumsulfate and then concentrated under a reduced pressure. The resultingresidue was purified by a column chromatography (eluent; hexane:ethylacetate=7:3-3:7) to obtain(R)-N-neopentyl-6-({tert-butoxycarbonyl-[(tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(3.40 g). In an ice bath, an ethyl acetate (5 ml) solution of thiscompound (250 mg) was mixed with 4 M hydrochloric acid-ethyl acetatesolution (15 ml) and, after removing the ice bath, stirred for 1 hour.The reaction mixture was dissolved in ethanol and then concentratedunder a reduced pressure. By washing the thus obtained crystals with amixed solvent of ethanol and ethyl acetate, the title compound (175 mg)was obtained.

¹H-NMR (DMSO-d₆); 0.94 (s, 9H), 1.50-1.60 (m, 1H), 1.77-1.88 (m, 2H),1.94-2.04 (m, 1H), 2.80-2.89 (m, 1H), 2.97-3.06 (m, 1H), 3.14 (d, 2H),3.68-3.74 (m, 1H), 3.77-3.83 (m, 1H), 4.15-4.23 (m, 1H), 7.60 (dd, 1H),7.78 (d, 1H), 8.11 (s, 1H), 8.89-8.96 (m, 1H), 9.34 (s, 1H)

MS (FAB+); 401 (M+1)

The compounds of Examples 48, 49, 50, 52, 53, 55, 57, 58, 59, 69, 70,72, 73, 77, 78 and 80 were synthesized by the same method of Example 24.

Example 266-{[(1,3-Dioxolan-2-ylmethyl)amino]methyl}-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example 9(315 mg) was mixed with acetic acid (285 μl) and1,3-dioxolan-2-ylmethylamine (282 μl), and the mixture was stirred atroom temperature for 1 hour. Subsequently, this was mixed with sodiumtriacetoxyborohydride (382 mg) and further stirred at room temperaturefor 1.5 hours. After completion of the reaction, the reaction mixturewas mixed with saturated sodium bicarbonate aqueous solution andstirred, and then the insoluble matter was filtered and washed withchloroform. The filtrate and washing solution were combined andconcentrated under a reduced pressure, and then the resulting residuewas purified by a column chromatography (eluent; chloroform:methanol:29% aqueous ammonia=100:0:0-93:7:0.7-90:10:1). By making the thusobtained product into hydrochloride in the usual way and recrystallizingit from ethanol and ethyl acetate, the title compound (364 mg) wasobtained.

¹H-NMR (DMSO-d₆); 0.94 (s, 9H), 3.04-3.11 (m, 2H), 3.14 (d, 2H),3.85-3.92 (m, 2H), 3.96-4.02 (m, 2H), 4.33-4.41 (m, 2H), 5.24 (t, 1H),7.63 (dd, 1H), 7.79 (d, 1H), 8.15 (d, 1H), 9.07 (t, 1H), 9.46 (s, 1H),9.64 (br, 2H)

MS (FAB+); 403 (M+1)

Example 28N-Neopentyl-6-({[(tetrahydro-2H-pyran-4-yl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example 9(315 mg) was mixed with acetic acid (285 μl) and(tetrahydropyran-4-yl)methylamine (346 mg), and the mixture was stirredat room temperature for 2 hours. Subsequently, this was mixed withsodium triacetoxyborohydride (382 mg) and further stirred at roomtemperature for 1 hour. After completion of the reaction, the reactionmixture was mixed with saturated sodium bicarbonate aqueous solution andstirred, and then the insoluble matter was filtered and washed withchloroform. The filtrate and washing solution were combined andconcentrated under a reduced pressure, and then the resulting residuewas purified by a column chromatography (eluent; chloroform:methanol:29% aqueous ammonia=100:0:0-93:7:0.7-90:10:1). By making the thusobtained product into hydrochloride in the usual way and recrystallizingit from ethanol and ethyl acetate, the title compound (260 mg) wasobtained.

¹H-NMR (DMSO-d₆); 0.94 (s, 9H), 1.14-1.26 (m, 2H), 1.70 (d, 2H),1.95-2.10 (m, 1H), 2.73-2.84 (m, 2H), 3.13 (d, 2H), 3.26 (t, 2H), 3.83(dd, 2H), 4.32 (br, 2H), 7.67 (br, 1H), 7.96 (br, 1H), 8.46 (br, 1H),9.01 (br, 1H), 9.52 (br, 3H)

MS (FAB+); 415 (M+1)

Example 31N-(1,3-Dioxolan-2-ylmethyl)-N-methyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide

A dichloroethane (15 ml) solution of the compound of Reference Example11 (440 mg) was mixed with acetic acid (362 μl), 3-amino-oxetanehydrochloride (417 mg) and triethylamine (530 μl), and the mixture wasstirred at room temperature for 1 hour. Subsequently, this was mixedwith sodium triacetoxyborohydride (485 mg) and further stirred at roomtemperature for 4 hours. After completion of the reaction, the reactionmixture was mixed with saturated sodium bicarbonate aqueous solution andstirred, and then the insoluble matter was filtered and washed withchloroform. The filtrate and washing solution were combined andconcentrated under a reduced pressure, and then the resulting residuewas purified by a column chromatography (eluent; chloroform:methanol:29% aqueous ammonia=100:0:0-93:7:0.7-90:10:1). By recrystallizing theformed substance from 2-propanol and diisopropyl ether, the titlecompound (132 mg) was obtained.

¹H-NMR (DMSO-d₆); 3.25-4.00 (m, 12H), 4.33 (t, 2H), 4.58 (t, 2H), 5.08(br, 1H), 7.33 (dd, 1H), 7.61 (d, 1H), 8.05 (br, 1H), 9.01 (br, 1H)

MS (FAB+); 403 (M+1)

The compounds of Examples 30, 33, 36, 38, 40, 41, 42, 43, 44, 45, 46 and47 were synthesized by the same method of Example 31.

Example 34N-(1,3-Dioxolan-2-ylmethyl)-N-methyl-6-{[(R)-(tetrahydro-3-furyl)amino]methyl}thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example11 (439 mg) was mixed with acetic acid (362 μl),(R)-(tetrahydrofuran-3-yl)amine p-toluenesulfonate (988 mg) andtriethylamine (530 μl), and the mixture was stirred at room temperaturefor 1 hour. Subsequently, this was mixed with sodiumtriacetoxyborohydride (485 mg) and further stirred at room temperaturefor 2 hours. After completion of the reaction, the reaction mixture wasmixed with saturated sodium bicarbonate aqueous solution and stirred,and then the insoluble matter was filtered and washed with chloroform.The filtrate and washing solution were combined and concentrated under areduced pressure, and then the resulting residue was purified by acolumn chromatography (eluent; chloroform:methanol: 29% aqueousammonia=100:0:0-93:7:0.7-90:10:1). By making the thus obtained productinto hydrochloride in the usual way and recrystallizing it from ethanoland ethyl acetate, the title compound (400 mg) was obtained.

¹H-NMR (DMSO-d₆); 2.10-2.30 (m, 2H), 3.00-4.00 (m, 14H), 4.25-4.35 (m,2H), 5.09 (br, 1H), 7.76 (d, 1H), 7.81 (d, 1H), 8.36 (s, 1H), 9.20 (br,1H), 9.95 (br, 2H)

MS (FAB+); 417 (M+1)

Example 35N-(1,3-Dioxolan-2-ylmethyl)-N-methyl-6-({[((R)-tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

An ethanol (50 ml) solution of the compound of Reference Example 7 (800mg) was mixed with 4 M hydrochloric acid-ethyl acetate solution (70 ml)and stirred for 3 hours. After completion of the reaction, the reactionmixture was concentrated under a reduced pressure and dried under areduced pressure, thereby obtaining6-({[(R)-(tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride (753 mg). A DMF (20 ml) suspension of this compound (375mg) was mixed with 1-hydroxybenzotriazole (163 mg) and1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride (533 mg),and the mixture was stirred at room temperature for 2 hours. Thereaction mixture was mixed withN-(1,3-dioxolan-2-ylmethyl)-N-methylamine (317 μl) and further stirredat room temperature for 2.5 hours. After completion of the reaction, thereaction mixture was poured into water, and the water layer wasextracted with ethyl acetate. The organic layer was collected, washedwith water and saturated brine, dried with anhydrous sodium sulfate andthen concentrated under a reduced pressure. The resulting residue waspurified by a column chromatography (eluent;chloroform:methanol=100:0-90:10-85:15). By making the product intohydrochloride in the usual way and recrystallizing it from ethanol andacetonitrile, the title compound (28 mg) was obtained.

¹H-NMR (DMSO-d₆); 1.51-1.60 (m, 1H), 1.76-1.92 (m, 2H), 1.95-2.04 (m,1H), 2.84-2.74 (m, 1H), 3.00-3.09 (m, 1H), 3.68-4.01 (m, 11H), 4.15-4.24(m, 1H), 4.25-4.36 (m, 2H), 5.09 (br, 1H), 7.61 (dd, 1H), 7.76 (d, 1H),8.20 (br, 1H), 8.95-9.50 (m, 3H)

MS (FAB+); 431 (M+1)

Example 37N-(1,3-Dioxolan-2-ylmethyl)-6-{[(1,3-dioxolan-2-ylmethyl)amino]methyl}-N-methylthiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example11 (345 mg) was mixed with acetic acid (285 μl) and2-aminomethyl-1,3-dioxolan (282 μl), and the mixture was stirred at roomtemperature for 1 hour. Subsequently, this was mixed with sodiumtriacetoxyborohydride (382 mg) and further stirred at room temperaturefor 1.5 hours. After completion of the reaction, the reaction mixturewas mixed with saturated sodium bicarbonate aqueous solution andstirred, and then the insoluble matter was filtered and washed withchloroform. The filtrate and washing solution were combined andconcentrated under a reduced pressure, and the resulting residue waspurified by a column chromatography (eluent; chloroform:methanol: 29%aqueous ammonia=100:0:0-93:7:0.7-90:10:1). By making the product intohydrochloride in the usual way and recrystallizing it from ethanol andethyl acetate, the title compound (363 mg) was obtained.

¹H-NMR (DMSO-d₆); 3.06-3.13 (m, 2H), 3.30-4.03 (m, 13H), 4.33 (br, 2H),5.10 (br, 1H), 5.25 (t, 1H), 7.67 (d, 1H), 7.79 (d, 1H), 8.27 (s, 1H),9.13 (br, 1H), 9.58 (br, 2H)

MS (FAB+); 433 (M+1)

Example 39N-(1,3-Dioxolan-2-ylmethyl)-N-methyl-6-({[(tetrahydro-2H-pyran-4-yl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A dichloroethane (15 ml) solution of the compound of Reference Example11 (345 mg) was mixed with acetic acid (285 μl) and(tetrahydropyran-4-yl)methylamine (346 mg), and the mixture was stirredat room temperature for 2 hours. Subsequently, this was mixed withsodium triacetoxyborohydride (382 mg) and further stirred at roomtemperature for 1 hour. After completion of the reaction, the reactionmixture was mixed with saturated sodium bicarbonate aqueous solution andstirred, and then the insoluble matter was filtered and washed withchloroform. The filtrate and washing solution were combined andconcentrated under a reduced pressure, and the resulting residue waspurified by a column chromatography (eluent; chloroform:methanol: 29%aqueous ammonia=100:0:0-93:7:0.7-90:10:1). By making the product intohydrochloride in the usual way and recrystallizing it from ethanol andethyl acetate, the title compound (309 mg) was obtained.

¹H-NMR (DMSO-d₆); 1.15-1.25 (m, 2H), 1.71 (d, 2H), 1.96-2.10 (m, 1H),2.76-2.84 (m, 2H), 3.26-4.06 (m, 18 H), 4.25-4.30 (m, 2H), 5.10 (br,1H), 7.73 (d, 1H), 7.79 (d, 1H), 8.29 (s, 1H), 9.14 (br, 1H), 9.44-9.62(m, 2H)

MS (FAB+); 445 (M+1)

Example 61N-(4-Methoxybutyl)-N-methyl-6-({[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride Example 64N-(4-Hydroxybutyl)-N-methyl-6-({[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (5 ml) solution of the compound of Reference Example 7 (400 mg)was mixed with 1-hydroxybenzotriazole (163 mg) and1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (535 mg) andstirred at room temperature for 40 minutes. The reaction mixture wasmixed with 4-amino-1-butanol (257 μl) and further stirred at roomtemperature for 20 minutes. After completion of the reaction, thereaction mixture was separated between layers using a mixture of waterand ethyl acetate, and the water layer was extracted with ethyl acetate.The organic layer was collected, washed with water, 1 M sodium hydroxideaqueous solution and saturated brine, dried with anhydrous sodiumsulfate and then concentrated under a reduced pressure. The resultingresidue was recrystallized from hexane and ethyl acetate to obtainN-(4-hydroxybutyl)-6-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(380 mg). Under ice-cooling, a DMF (10 ml) solution of this compound(360 mg) was mixed with methyl iodide (223 μl) and sodium hydride (60 to72%, oily) (52 mg) and stirred under ice-cooling for 1.5 hours. Aftercompletion of the reaction, the reaction mixture was poured intosaturated sodium bicarbonate aqueous solution and extracted with ethylacetate. The organic layer was washed with water and saturated brine,dried with anhydrous sodium sulfate and then concentrated under areduced pressure. The resulting residue was purified by a columnchromatography (eluent; chloroform:methanol=100:0-90:10-85:15) to obtainN-(4-methoxybutyl)-N-methyl-6-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(214 mg) andN-(4-hydroxybutyl)-N-methyl-6-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(165 mg). At room temperature, an ethanol (10 ml) solution ofN-(4-methoxybutyl)-N-methyl-6-({tert-butoxy-carbonyl-[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(200 mg) was mixed with 4 M hydrochloric acid-ethyl acetate solution (10ml) and stirred at room temperature for 2 hours. After completion of thereaction, the reaction mixture was concentrated under a reducedpressure. By making the resulting residue in a usual way intohydrochloride and recrystallizing it from ethanol and acetonitrile, thecompound of Example 61 (86.0 mg) was obtained.

¹H-NMR (DMSO-d₆); 1.49-1.70 (m, 5H), 1.76-1.90 (m, 2H), 1.95-2.04 (m,1H), 2.80-2.92 (m, 1H), 2.98-3.08 (m, 1H), 3.22-3.54 (m, 10H), 3.71 (dd,1H), 3.80 (dd, 1H), 4.17-4.35 (m, 3H), 7.67 (dd, 1H), 7.77 (d, 1H), 8.25(br, 1H), 9.06 (br, 1H), 9.34 (br, 1H), 9.67 (br, 1H)

MS (FAB+); 431 (M+1)

In addition, an ethanol (10 ml) solution ofN-(4-hydroxybutyl)-N-methyl-6-({tert-butoxycarbonyl-[((R)-tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(150 mg) was mixed with 4 M hydrochloric acid-ethyl acetate solution (10ml) at room temperature and stirred at room temperature for 2 hours.After completion of the reaction, the reaction mixture was concentratedunder a reduced pressure. By making the resulting residue intohydrochloride and recrystallizing it from ethanol and acetonitrile, thecompound of Example 64 (42.0 mg) was obtained.

¹H-NMR (DMSO-d₆); 1.41-2.03 (m, 8H), 2.82-2.92 (m, 1H), 2.99-3.08 (m,1H), 3.35-3.54 (m, 7H), 3.70 (dd, 1H), 3.80 (dd, 1H), 4.19-4.37 (m, 3H),7.68 (d, 1H), 7.78 (d, 1H), 8.28 (s, 1H), 9.09 (br, 1H), 9.35 (br, 1H),9.68 (br, 1H)

MS (FAB+); 417 (M+1)

The compounds of Examples 62, 65, 63, 66 and 67 were synthesized by thesame methods of Examples 61 and 64.

Example 76(R)-N-Methyl-N-(2-methyl-2-methylsulfanilpropyl)-6-({[(tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamidedihydrochloride

A DMF (5 ml) solution of(R)-N-(2-Methyl-2-methylsulfanilpropyl)-6-({tert-butoxycarbonyl-[(tetrahydro-2-furyl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(413 mg), which can be synthesized from the compound of ReferenceExample 7 and 2-methyl-2-methylsulfanilpropylamine by the same method ofExample 24, was mixed with methyl iodide (73 μl) and, in an ice bath,sodium hydride (60 to 72%, oily) (35 mg) was added thereto and stirredin the ice bath for 1 hour. After completion of the reaction, thereaction mixture was poured into saturated sodium bicarbonate aqueoussolution and extracted with ethyl acetate. The organic layer wascollected, washed with water and then with saturated brine, dried withanhydrous magnesium sulfate and then concentrated under a reducedpressure. The resulting residue was purified by a column chromatography(eluent; hexane:ethyl acetate=75:25-25:75) to obtain(R)-N-methyl-N-(2-methyl-2-methylsulfanilpropyl)-6-({tert-butoxycarbonyl-[(tetrahydro-2-furfuryl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide(398 mg). In an ice bath, ethyl acetate (5 ml) solution of this compound(398 mg) was mixed with 4 M hydrochloric acid-ethyl acetate solution (15ml) and, after removing the ice bath, stirred for 2 hours. The reactionmixture was dissolved by adding ethanol thereto and then concentratedunder a reduced pressure. By recrystallizing the thus obtained crystalsfrom ethanol and ethyl acetate, the title compound (318 mg) wasobtained.

¹H-NMR (DMSO-d₆); 1.29 (s, 6H), 1.51-1.61 (m, 1H), 1.78-1.89 (m, 2H),1.95-2.09 (m, 4H), 2.81-2.92 (m, 1H), 3.00-3.09 (m, 1H), 3.52 (br, 3H),3.67-3.74 (m, 3H), 3.77-3.84 (m, 1H), 4.16-4.24 (m, 1H), 4.27-4.33 (m,2H), 7.65 (dd, 1H), 7.78 (d, 1H), 8.24 (br, 1H), 9.15 (s, 1H)

MS (FAB+); 447 (M+1)

The compounds of Examples 51, 54, 56, 68, 71, 74, 75 and 79, weresynthesized by the same method of Example 76.

Structures and physical property values of the aforementioned examplesare shown in the following table.

TABLE 1

EX Ra- -Rb Salt MS 1

2HCl 427(M + 1) 2

free 399(M + 1) 3

2HCl 405(M + 1) 4

2HCl 403(M + 1) 5

2HCl 417(M + 1) 6

1.5fumarate 387(M + 1) 7

free 415(M + 1) 8

2HCl 401(M + 1) 9

2HCl 401(M + 1) 10

2HCl 415(M + 1) 11

2HCl 415(M + 1) 12

2HCl 417(M + 1) 13

2HCl 429(M + 1) 14

2HCl 449(M + 1) 15

2HCl 415(M + 1) 16

2HCl 443(M + 1) 17

2HCl 429(M + 1) 18

2HCl 459(M + 1) 19

3HCl 444(M + 1) 20

2HCl 375(M + 1) 21

free 373(M + 1) 22

2HCl 387(M + 1) 23

2HCl 387(M + 1) 24

2HCl 401(M + 1) 25

2HCl 401(M + 1) 26

2HCl 403(M + 1) 27

2HCl 401(M + 1) 28

2HCl 415(M + 1) 29

3HCl 430(M + 1) 30

2HCl 405(M + 1) 31

free 403(M + 1) 32

(L)-tartarate 430(M + 1) 33

2HCl 417(M + 1) 34

2HCl 417(M + 1) 35

2HCl 431(M + 1) 36

2HCl 431(M + 1) 37

2HCl 433(M + 1) 38

2HCl 431(M + 1) 39

2HCl 445(M + 1) 40

3HCl 460(M + 1) 41

free 387(M − 1)FAB(−) 42

2HCl 417(M + 1) 43

2HCl 417(M + 1) 44

2HCl 418(M)El 45

2HCl 416(M)El 46

2HCl 431(M + 1) 47

3HCl 446(M + 1) 48

2HCl 373(M + 1) 49

2HCl 387(M + 1) 50

2HCl 401(M + 1) 51

2HCl 415(M + 1) 52

2HCl 429(M + 1) 53

2HCl 415(M + 1) 54

2HCl 415(M + 1) 55

2HCl 415(M + 1) 56

2HCl 415(M + 1) 57

2HCl 429(M + 1) 58

2HCl 383(M + 1) 59

2HCl 403(M + 1) 60

2HCl 417(M + 1) 61

2HCl 431(M + 1) 62

2HCl 445(M + 1) 63

2HCl 459(M + 1) 64

2HCl 417(M + 1) 65

2HCl 431(M + 1) 66

2HCl 445(M + 1) 67

2HCl 457(M + 1) 68

2HCl 429(M + 1) 69

3HCl 416(M + 1) 70

3HCl 430(M + 1) 71

2HCl 402(M + 1) 72

2HCl 383(M + 1) 73

2HCl 398(M + 1) 74

2HCl 419(M + 1) 75

2HCl 433(M + 1) 76

2HCl 447(M + 1) 77

2HCl 463(M + 1) 78

2HCl 433(M + 1) 79

HCl 427(M + 1) 80

2HCl 459(M + 1) 81

2HCl 427(M + 1)(Test Methods)1. The mGluR 1 Binding Activity

Effect of the compounds of the invention upon mGluR 1 was verified inaccordance with the method described in the Patent Reference 3.

The action of the compounds of the invention was verified by a bindingtest which uses a tritium-labeled form of6-amino-N-cyclohexyl-N,3-dimethylthiazolo[3,2-a]benzimidazole-2-carboxamide(specific activity; 81 Ci/mmol (Amersham)) that shows selective andstrong action upon mGluR 1.

The aforementioned compound has a high inhibitory activity of IC₅₀=24 nMfor the reaction of glutamic acid in a phosphatidylinositol (PI)hydrolysis system which uses an mGluR 1 α expression cell (Nature, 383,89-92, 1996).

(Preparation of Rat Cerebellum P2 Membrane Fraction)

Each rat (Wistar, male, 9 to 12 weeks of age) was decapitated to excisethe cerebellum. After weight measurement, this was homogenized in 7 to10 volumes of 0.32 M sucrose solution. After 15 minutes ofcentrifugation at 900×g, the supernatant was preserved in a container(in ice). The precipitate was again homogenized in 0.32 M sucrosesolution of the same volume of the first time and centrifuged at 900×gfor 15 minutes. The supernatant obtained this time was combined with thepreviously obtained supernatant and centrifuged at 15,000×g for 20minutes. The precipitate was homogenized in 5 mM Tris-HCl, pH 7.4, andcentrifuged at 15,000×g for 15 minutes. This step was repeated again.The precipitate was homogenized in 50 mM Tris-HCl, pH 7.4, andcentrifuged at 15,000×g for 15 minutes. The precipitate was homogenizedin an appropriate amount of 50 mM Tris-HCl, pH 7.4, subdivided intosmall portions and then preserved at −80° C.

(Binding Test)

As the assay buffer, 50 mM Tris-HCl, 2.5 mM CaCl₂, pH 7.4, was used.[³H]-(6-Amino-N-cyclohexyl-N,3-dimethylthiazolo[3,2-a]benzimidazole-2-carboxamide)(specific activity; 81 Ci/mmol; Amersham), a test compound and about 0.1mg of the rat cerebellum P2 membrane fraction were suspended to a totalvolume of 100 μl in a 96 well microplate and then incubated at roomtemperature (about 25° C.) for 45 minutes. Completion of the incubationwas carried out by a filtration method using Whatman GF/B filter.Quantity of the radioactivity was measured using a liquid scintillationcounter. About 20 nM of[³H]-6-amino-N-cyclohexyl-N,3-dimethylthiazolo[3,2-a]benzimidazole-2-carboxamidewas used in the competitive test, and the specific binding was definedas a portion of the total binding, which was replaced by 10 μM of6-{[(2-methoxyethyl)amino]methyl}-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide(Patent Reference 3, the compound described in Example 75). Evaluationof the test compound was carried out by calculating the ratio of bindinginhibition upon the specific binding.

Determination of protein was carried out using BIO-RAD DC protein assay(BIO-RAD). Bovine serum albumin was used as the standard substance.

The results are shown in Table 4.

REFERENCE DOCUMENT

-   Thomsen C., Mulvihill E. R., Haldeman B., Pickering D. S.,    Hampson D. R. and Suzdak P. D., A pharmacological characterization    of the mGluR 1 alpha subtype of the metabotropic glutamate receptor    expressed in a cloned baby hamster kidney cell line., Brain Res.,    Aug. 13, 1993, 619(1-2), 22-8    2. Inhibitory Effect Upon Neuropathic Pain    1) Streptozotocin (to be Referred to as STZ Hereinafter)—Induced    Diabetes Model

The test was carried out by modifying a part of a report (Pharmacol.Biochem. Behav., 39, 541-544, 1991). At a dose of 200 mg/kg, STZ wasintraperitoneally administered to each of ICR mice of 4 weeks of age. Apreliminary test of a tail pinch test was carried out in the afternoonof the day 2 weeks after the administration, and only animals showing areaction latency of 3 seconds or less were submitted to the next day'stest. Each compound was loaded by 10 mg/kg of oral administration, andthe tail pinch test was carried out after 30 minutes of theadministration to calculate a difference from the value of latencymeasured in the preliminary test.

In this connection, normal mice unloaded with STZ show a reactionlatency of 6 to 7 seconds in average by this test. STZ-loaded micehaving a reaction latency of 3 seconds or less in which distinctreduction in the pain threshold was observed were used in the test ofthis time.

The results are shown in Table 4. An average reaction latency differenceof 2 seconds or more was defined as + (positive action), and 1.5 secondsor more and less than 2 seconds as ± and less than 1.5 seconds as − (noaction).

TABLE 4 mGluR 1 Average binding reaction test; IC₅₀ Dose latency Example(nM) (p.o.) difference  6 2  10 mg/kg +  7 9  10 mg/kg + 11 3  10mg/kg + 15 26  10 mg/kg + 17 6  10 mg/kg + 23 30  10 mg/kg + 24 11  10mg/kg + 26 8  10 mg/kg + 28 48  10 mg/kg + 31 43  10 mg/kg + 34 37  10mg/kg + 35 12  10 mg/kg + 37 8  10 mg/kg + 39 26  10 mg/kg + Controlcompd. A 22 100 mg/kg − Control compd. B 25 100 mg/kg − Control compd. C7 100 mg/kg − Control compd. D 25 100 mg/kg −

-   Control compound. A: Patent Reference 4, the compound disclosed in    Example 112-   Control compound. B: Patent Reference 4, the compound disclosed in    Example 116-   Control compound. C: Patent Reference 4, the compound disclosed in    Example 126-   Control compound. D: Patent Reference 4, the compound disclosed in    Example 133

Based on the above tests, it was confirmed that the compounds of theinvention are compounds which specifically bind to mGluR 1.

Also, it was confirmed that the compounds of the invention have theeffect to treat diabetes mellitus-induced neuropathic pain by their oraladministration.

In addition, it was confirmed that the compounds of the invention arecompounds whose oral activity is 10 times or more superior to thecontrol compounds having analogous structures but no aniline amino groupand therefore are compounds useful as oral preparations.

2) L5/L6 Spinal Nerves-Ligated Rat

The test was carried out by modifying a part of a report (PAIN, 50,355-363, 1992). Using SD rats, left side hip nerves (L5 and L6) wereligated with a silk thread under pentobarbital anesthesia. The followingtest was carried out during a period of from on the 7th day to the 14thday after the operation.

Each compound was orally administered, and the von Frey hair (VFH) testwas carried out 30 minutes thereafter to calculate the pain thresholdvalue against mechanical nocuous stimulus. The measurement was carriedout on the left and right hind legs.

In this connection, there was no difference in the pain threshold valueof pseudo-operation rats between left and right hind legs, which was17-20 g (log (g):1.23-1.30, and reduction of the pain threshold valueagainst mechanical nocuous stimulus was observed in the operated sideleg of the L5/L6 spinal nerves-ligated rat.

The significant difference test was carried out using the Dunnett methodon respective left and right legs between the control group andcompound-administered group.

Results

The compounds of Examples 15, 17 and 28 showed their efficacy upon thethreshold value reduction in the operated side by 30 mg/kg of oraladministration.

It was confirmed based on this that the compounds having mGluR 1antagonism have a therapeutic effect for a neuropathic pain caused bynerve compression.

3. Genetic Toxicity

Gene mutation inducing ability of the compounds of the invention wasverified by a reverse mutation test which uses a bacterium.

The test was carried out in accordance with the genetic toxicity testguideline of drugs (Iyakushin No. 1604, Nov. 1, 1999) by apre-incubation method in the presence and absence of a metabolicactivation system. However, Salmonella typhimurium TA 98 and TA 100alone were used as the test strains.

(Reverse Mutation Test Using a Bacterium)

A 0.5 ml portion of 0.1 M sodium phosphate buffer (pH 7.4), 0.1 ml of anovernight-cultured test strain suspension and 0.1 ml of a solution of asubstance to be tested were put into a test tube and shaken (60reciprocation/min) at 37° C. for 20 minutes, and then 2 ml of soft agarkept at about 45° C. was added thereto and the mixture was spread on aminimal glucose agar plate medium (plate) and cultured at 37° C. forabout 48 hours. In the case of the metabolic activation test, the sameprocedure was carried out by adding the same volume of S9Mix instead ofthe 0.1 M sodium phosphate buffer.

Results

The S9Mix used in the metabolic activation test was prepared usingS-9/cofactor A set (a 9,000×g supernatant of homogenate of the rat liverin which drug metabolizing enzymes had been induced using phenobarbitaland 5,6-benzoflavone and Cofactor, for Ames test use, Oriental YeastCo., Ltd.). The amount of S9 in S9Mix was set to 0.1 ml/ml. Dimethylsulfate was used as the solvent.

The number of colonies formed on the plate after 48 hours of culturingwas counted. When the number of reverse mutation colonies (averagevalue) on the plate treated with a substance to be tested was increasedto 2 times or more of the number of the solvent control reverse mutationcolonies (average value), and its dose-dependency was observed and thereproducibility was confirmed, it was judged that the compound has thegene mutation inducing ability.

While the aniline amino group-containing compounds A and B described inthe Patent Reference 2 have the oral activity equivalent to thecompounds of the invention (cf. Patent Reference 2), it was confirmed asa result of the above test that the compound A is positive in genemutation inducing ability.

On the other hand, it was confirmed that the compound of Example 12 ofthe invention has an oral activity similar to or larger than that of thecompounds described in the Patent Reference 2 (effective at 10 mg/kg),and its gene mutation inducing ability is also negative.

Accordingly, it was confirmed that the compounds of the invention areclinically useful compounds, because they have excellent oral activityand do not have gene mutation inducing ability.

INDUSTRIAL APPLICABILITY

The compounds of the invention are compounds useful as medicaments,because they are compounds which have excellent oral activity showingstrong action upon the metabotropic glutamate receptor and also haveexcellent therapeutic effect upon diabetic and nerve compression-inducedneuropathic pain. In addition, the compounds of the invention areclinically useful, because they are compounds which do not have anilineamino group and in which improvement of oral activity was achieved sothat they do not have gene mutation inducing ability based on theaniline amino group.

Accordingly, the compounds of the invention are useful as preventive ortherapeutic agents for diseases in which the mGluR 1 receptor isconsidered to be taking a role, such as epilepsy, pain, inhibition ofnerve cell death, benzodiazepine withdrawal syndrome, Parkinson disease,migraine, anxiety disorder, cerebral infarction (preferably an agent forpreventing development of infarct focus, which is administered acutephase of cerebral infarction) and a neuropathic pain (preferably a painaccompanied by diabetic neuropathy, a neuralgia after shingles, acancerous pain or a postoperative chronic pain).

1. An aminomethyl-substituted thiazolobenzimidazole compound representedby the following formula (I) or a salt thereof

(wherein signs in the formula mean as follows; R¹: an oxygen-containingsaturated hetero ring- which may be substituted, Alk1: a lower alkylene,m: 0 or 1, Alk2: a lower alkylene which may be substituted with oxogroup, n: 0 or 1, X: a bond, O, S or NR⁵, R³: a lower alkyl or asaturated hetero ring-, and R², R⁴ and R⁵: the same or different fromone another and each represents H or lower alkyl, with the proviso thatR³ does not represent a lower alkyl when X is a bond and n is 1).
 2. Acompound selected from the group consisting ofN-methyl-N-neopentyl-6-[(oxetan-3-ylamino)methyl]thiazolo[3,2-a]benzimidazole-2-carboxamide;6-{[(1,3-dioxolan-2-ylmethyl)amino]methyl}-N-methyl-N-neopentylthiazolo[3,2-a]benzimidazole-2-carboxamide;andN-neopentyl-6-({[tetrahydro-2H-pyran-4-yl)methyl]amino}methyl)thiazolo[3,2-a]benzimidazole-2-carboxamide;or a salt thereof.
 3. A medicament which comprises theaminomethyl-substituted thiazolobenzimidazole compound described inclaim 1 or a salt thereof as the active ingredient.